Recently a number of robotic intervention systems for magnetic resonance image (MRI) guided needle placement in the prostate have been reported. In MRI-guided needle interventions, after a needle is inserted, the needle position is often confirmed with a volumetric MRI scan. Commonly used titanium needles are not directly visible in an MR image, but they generate a susceptibility artifact in the immediate neighborhood of the needle. This paper reports the results of a quantitative study of the relationship between the true position of titanium biopsy needle and the corresponding needle artifact position in MR images, thereby providing a better understanding of the influence of needle artifact on targeting errors. The titanium needle tip artifact extended 9 mm beyond the actual needle tip location with tendency to bend towards the scanner’s B0 magnetic field direction, and axially displaced 0.38 mm and 0.32 mm (mean) in scanner’s frequency and phase encoding direction, respectively.
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